The broad objective of the proposed work is the elucidation of the manner in which fat mobilization is regulated in man. In pursuing this goal, we are using an in vitro system of isolated adipocytes. We have learned that human adipocytes have both alpha and beta adrenergic receptors that appear to mediate divergent effects on adenylyl cyclase, cyclic AMP and lipolysis. Free fatty acids inhibit lipolysis as does insulin. We intend to define the site of action of insulin and the interrelationship between alpha adrenergic receptors and adenylyl cyclase. When appropriate, complementary studies with animal models are done.